I have a kind of weird question. But this wont be a harder one.

Actually, i feel it is incomplete. I don't have much experience on statistics. But some advance user will be able to understand this (may be guess the incomplete parts). I'll post all the information i have. Please try to give an answer to this.

This is about a set of calls..

Number of calls taken, $N = 1000$

Mean value, $\mu = 240$

Standard deviation, ${\sigma} = 50$ (Can this be in seconds???)

Given above details, the question is something like "What is the ***" of 1% of all are shorter: And the answer is 124s

Can someone please help me with this. Please explain what can be the question and show me how to solve it. I have some some knowledge on statistics and normal distribution..

Any help is greatly appreciated...

Thank you!

  • $\begingroup$ As a well appreciated manner in these Q&A-sites: would you please mind to add some more info about the problem in the title of your question? $\endgroup$ Commented Aug 1, 2012 at 11:21

1 Answer 1


Consider the normal distribution with mean 240 and standard deviation 50. Then 123.68 (so approx. 124) is the 1%-quantile of this distribution. So if you assume that your observations are normally distributed with the above mean and standard deviation, approximately 1% of them should be 124 or less. So, loosely speaking, the question your are looking for might be something like "What is the length x, such that 1% of the observations are shorter than x?"

  • $\begingroup$ Yeah, I guess you are correct. Thanks for that! (I've learn stat in a last semester, but haven't used recently..:D) $\endgroup$
    – Anubis
    Commented Aug 1, 2012 at 10:48

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